1. Field of the Invention
The present invention relates to an electromagnetically operated electric switch, for example a contactor, having at least one movable contact attached in a contact carrier, which via rotatable arms are connected to two similar magnetic cores of an operating magnet. The two cores are movable in opposite directions along a line which is substantially perpendicular to the direction of movement of the contact carrier.
2. Prior Art
A contactor of the above-mentioned kind is previously known from Swiss Pat. No. 349,324. Compared with the most frequently used contactor designs, which have a stationary magnetic core with a magnet armature which moves in the same direction as the contacts, the design described above has several advantages:
(a) Contact bounce caused by the armature movement is completely eliminated.
(b) A very considerable dynamic stability, i.e. shock-proofness, is obtained both in the closed and open position and in all directions.
(c) Because of the dynamic stability in open position, the initial attractive force of the magnet can be considerably reduced and the magnet be made smaller.
(d) Through the gradual rotation of the arms, the gear ratio between the magnet movement and the contact movement is changed so that the force on the contact carrier is increased towards the end of the closing movement.
In the prior art design mentioned above, the magnetic cores are guided in slots in the contactor stand. Such a guide is subjected to considerably wear, since the cores have a relatively great weight. This means that only a small part of the mechanical life of 10-30 million of operations, stipulated for certain contactors, can be achieved. Also a construction in which the magnetic cores are suspended by means of rotatably links has a limited life, since the bearings of the links are worn out prematurely.